Resistance unit for electric heaters and regulating resistances



- W. SCHULZ. RESISTANCE UNIT FOR ELECTRIC HEATERS AND REGULATINGRESISTANCES.

APPLICATION man JUNE 11. 1916.

1,911 3,939. v Patented Apr. 25, 1922.

UNITED STATES PATENT OFFICE.

WILLY SCHULZ, OF FRANKFORI-ON-THE-MAIN, GERMANY, ASSIGNOR TO PROME-THEUS, FABRIK-ELEKTRISCHER KOCK- & HEIZAPPARATE, GESELLSCI-IAFT MITBESCHRANKTER HAFTUN G, CF FRANKFORT-ON THEMAIN, GERMANY.

RESISTANCE UNIT FOR ELECTRIC HEATERS AND REGULATING RESISTANCES.

Specification of Letters Patent. i Patgnted Apr, 25, 1922, Applicationfiled June 17, 1916. Serial No. 104,266.

(GEANTED UNDER THE IlROVISIONS OF THE ACT OF MARCH 3, 1921,41 STAT. In,1313-) To all whomit may concern:

. Be it known that I, VVVILLY, SoHULz, a subject of the German Emperor,and a resident of Frankfort-on-the-Main, Germany, have invented certainnew and useful Improvements in a Resistance Unit for Electric Heatersand Regulating Resistances, of which the following is a specification.

In the construction of electric heating a'pparatus including resistanceand regulating units the means employed for supporting or securing theresistance material in position is of the greatest importance.

'Such' resistance units are commonly formed of coils of round wire,metal tape or tubes and are only secured toa support at their ends. Theeli'ect of blows or jars to which such apparatus is necessarilysubjected causes such oscillation of the coils that the members thereoffrequently contact, producing short circuits and shunts, especially whenthe coils are expanded or extended by the heat due to the passing ofcurrent therethrough. This is particularly .true when the units are madeof thin metal such as required. for obtaining a high-ohmage.

With a view of overcoming this trouble, it has been proposed to wind theresistance material upon cores or bodies of insulating material ofvarious forms and in some instances provided with grooves to receive thewire or tape. However, even with such constructions the expansion of themetal is often sufficient to produce such deflection of the members ofthe coil as to cause contact and resulting short circuiting.

If the members of the coils are separated to such an extentthatundesirable contact between them is avoided the device must necesarily be so large as to render itunsuitable for many uses.

Various other expedients have been tried to avoid the hereinbefore notedobjections. For example, the resistance material has been embedded inenamel or secured to its support by such a substance or cement. The.

difference 1n expansion of the materials results in loosening theconnection between the resistance material and its support and thereforesuch an arrangement is not satisfactory.

By the present invention, the objections incident to prior constructionsare overcome and a simple, compact, resistance unit is provided in whichthe danger of short circuiting due to expansion of the coils is entirelyobviated. 1

In the accompanying drawing;

Figure 1 is an elevation of the lower end of an embodiment of theinvention;

Figure 2 is a horizontal sectional view on the line IIII of Figure" 1; i

Figure 3 isfa similar view, some' o fithe parts being on an enlargedscale, showing elements. j a

Referr ng to the drawing, the resistance conductonl 1s a flat band orstrip which is the preliminary assembling jolt the several 2 bent backand forth. into column form, the

members of each section of such conductor extending betweenclampingdevices shown as bars that extend longitudinally of theresistance column and of U-shape in cross section. 7

The clamping bars 2 are insulated from the adjacent surface of the coil1 by any suitable means, as for example, strips of mica 3; andbetween'the inner faces of the coil sections are arranged strips 4: of asbestosor other insulating material. c

In forming the coil the metal band 1 is wound about two yieldingpins orguides 5 and after the parts 2, 3 and 4 are properly assembled themembers of each section of the conductor are drawn toward each other bythe action of suitable screws on the clamping bars until such membersare held in close contact with the compressed or compacted insulatingstrips 4.

The terminal coils or members of the resistance coil are provided withsuitable means for connecting them with the line wires of an electriccircuit. Figure 2 shows two different forms of terminal connection,namely, a tubular connector 8 and a threaded bolt S provided withsuitable nuts. A's shown these terminal connections may be mounted on ablock 7 of insulating material attached to one of the clamping bars 2.

The terminal of the coil remote from the block 7 may be electricallyconnected with one of the connectors 8, 8 by a conductor 9 which ispositioned between the asbestos as preferred.

that can be connected in series or parallel By this arrangement a conductor of certain size and resistance may be employed for currents ofdifferent voltage. For example, the two halves of a coil may beconnected in parallel for a 110 volt current or in series for 220 volts.

The form of the clamping bars 2 is of considerable importance. The ribsor walls oi? the channel bars being directed outward act to carry theheat away so thatportions ot' the coil not directly exposed to the airmay be kept suitably 0001.

A resistance unit constructed in accordance with the invention may bereadily immersed in an oil bath to heat it or provide anexplosion-proof, oil cooled apparatus.

Having thus described the invention What is claimed is:

1. A resistance unit comprising a resistance conductor bent back andforth into column form, strips oi insulating material Within andextending throughout the length of said column, and means engaging bothmembers of each section of the conductor and compressing the insulatingmeans between them.

2. A resistance unit comprising a resistance conductor bent bacl: andforth into column lorm, strips of insulating .i'i'iaterial. within andextending longitudinally of said column, clamping bars arrangedexteriorly oi the column and insulated therefrom, and means connectingthe clamping bars adapted to cause the members of each section of theconductor to compress the intermediate strips of insulating material.

' 3. A resistance unit comprising a resistance conductor bent back andforth into column form, strips of asbestos extending longitudinally ofthe column between the members of each section oi? the conductor,clamping bars arranged exterior-1y ol': the column and extendingparallel to said asbestos strips, means insulating the bars from theconductor. and means connecting said bars and acting to cause them tocompress the conductor and intermediate asbestos strips.

in testimony Whereoi I affix my signature in presence of two Witnesses.

\VILLY SCHULZ.

lVitnesses ERWIN Drrrnn, CARL GRUND.

